Procedure for checking the functionality of an electric heating device

Abstract

A procedure for checking the functionality of an electric heating device ( 10 ) with at least one PTC-element ( 13, 14 ) is suggested. The electric heating device ( 10 ) is operated at a battery voltage. When controlling the heating device ( 10 ) it is impinged with a current and at least one measuring value is detected, which represents the current that flows through the heating device. The measuring value for the current is compared to at least one reference value with a default tolerance width while considering the battery voltage. In the case of a measuring value that deviates from the reference value an error can be assumed.

1. A procedure for checking the functionality of an electric heating device with at least one PTC-element, wherein the heating device is operated at a battery voltage and impinged with a current, wherein at least one measuring value is detected, which represents the current that flows through the heating device, wherein the measuring value for the current is compared to at least one reference while considering the battery voltage and in the case of a deviation of the measuring value from the reference value with a default tolerance width an error is assumed. 
     
     
       2. The procedure according to  claim 1  is wherein the comparison of the measuring value and the reference value the maximum current peak of the total current is used. 
     
     
       3. The procedure according to  claim 1 , wherein the heating device is a heating device for a tank, wherein the tank is preferably provided for storing reducing agent, in particular an aqueous urea-water-solution. 
     
     
       4. The procedure according to  claim 3 , wherein different reference values are considered for different tank temperatures. 
     
     
       5. The procedure according to  claim 1 , wherein in the case of a diagnosis “errorless” the measuring value is used for updating the reference values. 
     
     
       6. A computer program, which carries out all steps of a procedure according to  claim 1  if it runs on an arithmetic unit or control unit. 
     
     
       7. A computer program product with a program code that is stored on a machine-readable device for implementing the procedure according to  claim 1  if the program is carried out in an arithmetic unit or a control unit.